CN113465230A - Oil return control method for refrigeration system and refrigeration system - Google Patents
Oil return control method for refrigeration system and refrigeration system Download PDFInfo
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- CN113465230A CN113465230A CN202110721923.6A CN202110721923A CN113465230A CN 113465230 A CN113465230 A CN 113465230A CN 202110721923 A CN202110721923 A CN 202110721923A CN 113465230 A CN113465230 A CN 113465230A
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- 238000005057 refrigeration Methods 0.000 title claims abstract description 84
- 238000000034 method Methods 0.000 title claims abstract description 48
- 230000002708 enhancing effect Effects 0.000 claims description 11
- 239000003921 oil Substances 0.000 description 375
- 239000010687 lubricating oil Substances 0.000 description 33
- 239000003507 refrigerant Substances 0.000 description 14
- 239000002199 base oil Substances 0.000 description 11
- 239000007788 liquid Substances 0.000 description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 239000000314 lubricant Substances 0.000 description 8
- 239000000243 solution Substances 0.000 description 7
- 239000011521 glass Substances 0.000 description 4
- 238000005461 lubrication Methods 0.000 description 3
- 239000000498 cooling water Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 230000001050 lubricating effect Effects 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 230000003014 reinforcing effect Effects 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 239000010963 304 stainless steel Substances 0.000 description 1
- 229910000589 SAE 304 stainless steel Inorganic materials 0.000 description 1
- 238000004378 air conditioning Methods 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B31/00—Compressor arrangements
- F25B31/002—Lubrication
- F25B31/004—Lubrication oil recirculating arrangements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B43/00—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat
- F25B43/02—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat for separating lubricants from the refrigerant
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Power Engineering (AREA)
- Control Of Positive-Displacement Pumps (AREA)
Abstract
The invention relates to an oil return control method for a refrigerating system and the refrigerating system, and aims to solve the problem that the refrigerating system cannot return oil in time in the prior art. For this purpose, the oil return control method of the invention comprises the following steps: detecting an oil level height within the oil separator during operation of the refrigeration system; comparing the oil level height to the first oil level height and the second oil level height; controlling the on-off of the first oil level switch and the second oil level switch based on the comparison result; controlling the first and second intensifier solenoid valves to be closed and opened based on the on-off condition. By using the oil return control method, the refrigeration system can return oil to the compressor in time based on the height of the oil level in the oil separator, so that the oil return time is more accurate, and the oil return efficiency is obviously improved.
Description
Technical Field
The invention relates to a refrigeration system, in particular to an oil return control method for the refrigeration system and the refrigeration system.
Background
A refrigeration system generally includes four basic components, a compressor, a condenser, a throttle mechanism, and an evaporator, which form a circuit that allows a refrigerant to circulate therein, and compresses a low-temperature and low-pressure gas refrigerant into a high-temperature and high-pressure gas refrigerant using the compressor. Compressors, such as scroll compressors, centrifugal compressors, screw compressors, and the like, often require lubricating oil to provide lubrication and seal protection to the moving parts thereof during operation. Therefore, when the compressed high-temperature and high-pressure gas refrigerant is discharged from the compressor very quickly, the lubricant oil in the compressor is easily formed into oil vapor and oil droplet particles and discharged together with the gas refrigerant. When the lubricating oil enters the condenser and the evaporator together with the refrigerant, a layer of oil film is formed on the heat transfer wall surface, so that the thermal resistance is increased, the heat transfer effect of the condenser and the evaporator is reduced, and the refrigeration effect is reduced. Therefore, existing refrigeration systems, including but not limited to chiller, multi-split system, or other central air conditioning system, typically include an oil separator between the compressor and the condenser to separate the lubricating oil mixed in the refrigerant vapor. An oil separator is typically disposed on the discharge line connected to the discharge end of the compressor (and thus on the high pressure side of the refrigeration system) to separate the lubricant oil from the refrigerant before the lubricant oil-laden gaseous refrigerant enters the other major components of the refrigeration system.
The existing oil separator is generally provided with an oil return opening directly at the bottom of a cylinder body or a shell. The oil return port may be connected to a return pipe of the compressor on a low pressure side through an external oil return pipe to return the lubricating oil to the compressor by means of a high-low pressure difference. When the pressure difference is large, the lubricating oil in the oil separator can return oil quickly under the action of the pressure difference, and the lubricating requirement of the compressor can be met. When the pressure difference is small, the lubricating oil in the oil separator is not easy to suck out. Particularly, when the compressor is operated at a low frequency for a long time, the oil separator may not deliver the lubricating oil to the compressor in time, which may cause the compressor to operate in an oil-starved state. In addition, when the compressor runs in an oil-deficient state or needs oil return urgently, the requirement of quick oil return cannot be met only by one oil return pipeline, and therefore normal operation of the refrigeration system is affected.
Accordingly, there is a need in the art for a new solution to the above problems.
Disclosure of Invention
In order to solve the problems in the prior art, namely to solve the problem that the refrigeration system in the prior art cannot return oil in time, the invention provides an oil return control method for the refrigeration system. The refrigeration system comprises a compressor and an oil separator, wherein a first enhanced oil return opening and a second enhanced oil return opening which are spaced from each other are arranged at the bottom of the oil separator, the first enhanced oil return opening is connected with an air return pipe of the compressor through a first enhanced oil return pipeline with a first enhanced electromagnetic valve, the second enhanced oil return opening is connected with the air return pipe through a second enhanced oil return pipeline with a second enhanced electromagnetic valve, a first oil level switch corresponding to a first oil level height and a second oil level switch corresponding to a second oil level height are further arranged on the side wall of the oil separator, the second oil level height is higher than the first oil level height, and the oil return control method comprises the following steps:
detecting an oil level height within the oil separator during operation of the refrigeration system;
comparing the oil level height to the first oil level height and the second oil level height;
controlling the on-off of the first oil level switch and the second oil level switch based on the comparison result;
controlling the first and second intensifier solenoid valves to be closed and opened based on the on-off condition.
As can be appreciated by those skilled in the art, in the oil return control method for a refrigeration system of the present invention, the oil level height within the oil separator is detected during operation of the refrigeration system. Next, the measured oil level height is compared with preset first and second oil level heights. Then, the on/off of the first oil level switch and the second oil level switch is controlled based on the comparison result. And controlling the first and second intensifying electromagnetic valves to be closed and opened based on the on-off conditions of the first and second oil level switches. During operation of the refrigeration system, the oil level increases as the amount of lubrication oil in the oil separator increases (e.g., when the compressor is operating at low frequency for an extended period of time). At the moment, whether the refrigeration system needs oil return is judged by detecting the height of the oil level in the oil separator, so that the oil return time and the oil return amount can better meet the actual requirement. In addition, the oil separator is provided with the first oil level switch and the second oil level switch corresponding to different oil level heights so as to control the on-off of the corresponding reinforced oil return pipeline, differential oil return can be realized based on the change of the oil level heights, and the design of oil return control is more precise.
In the preferable technical solution of the oil return control method for the refrigeration system, the bottom is further provided with a basic oil return port, the basic oil return port is connected to the air return pipe through a basic oil return pipeline having a basic oil return solenoid valve, and the oil return control method further includes:
after the compressor is started, controlling the basic oil return electromagnetic valve to be closed;
detecting a pressure difference of the compressor;
and controlling the opening degree of the basic oil return electromagnetic valve based on the pressure difference. A basic oil return opening is formed in the bottom of the oil separator, and a basic oil return electromagnetic valve capable of controlling the opening degree of the basic oil return opening based on pressure difference is arranged on a basic oil return pipeline, so that the requirement of conventional oil return of a refrigeration system in a starting-up stage can be met.
In a preferable embodiment of the oil return control method for the refrigeration system, the step of controlling on/off of the first oil level switch and the second oil level switch based on the comparison result includes:
when the oil level height is smaller than the first oil level height, controlling the first oil level switch and the second oil level switch to be switched off;
when the oil level height is greater than or equal to the first oil level height and smaller than the second oil level height, controlling the first oil level switch to be closed and controlling the second oil level switch to be opened;
and when the oil level height is greater than or equal to the second oil level height, controlling the first oil level switch and the second oil level switch to be closed.
In the above-mentioned preferable technical solution of the oil return control method for the refrigeration system, when both the first oil level switch and the second oil level switch are turned off,
keeping the first and second intensifier solenoid valves open. When the first oil level switch and the second oil level switch are both turned off, the oil level in the oil separator is lower than the first oil level at the moment, more lubricating oil is in the compressor, and the conventional oil return through the basic oil return pipeline can meet the oil return requirement, so that the first enhancement electromagnetic valve and the second enhancement electromagnetic valve are kept turned off.
In the above-mentioned preferable technical solution of the oil return control method for the refrigeration system, when the first oil level switch is closed and the second oil level switch is opened,
after a first preset time period, controlling the first enhancement electromagnetic valve to be closed;
re-detecting an oil level height within the oil separator;
comparing the current oil level height to the first oil level height;
when the current oil level height is smaller than the first oil level height, the first oil level switch is turned off;
and after a second preset time period, controlling the first enhancing electromagnetic valve to be disconnected. When the first oil level switch is closed and the second oil level switch is opened, the oil level height in the oil separator is between the first oil level height and the second oil level height, and more lubricating oil is in the oil separator, so that the first enhancement electromagnetic valve is controlled to be closed, and the lubricating oil can flow out from the first enhancement oil return opening and flow to the air return pipe of the compressor along the first enhancement oil return pipeline. At this time, two oil return lines (a base oil return line and a first enhanced oil return line) are provided between the oil separator and the compressor, and the oil return rate is increased. When the re-detected oil level is lower than the first oil level, it is indicated that the oil amount can meet the lubrication requirement of the compressor at this time, and therefore the first intensifying electromagnetic valve is controlled to be turned off.
In a preferable embodiment of the oil return control method for a refrigeration system, when the current oil level height is equal to or greater than the first oil level height, the step of re-detecting the oil level height in the oil separator is repeated. And when the current oil level height is larger than or equal to the first oil level height, which indicates that more lubricating oil still exists in the oil separator at the moment, continuing to keep the first enhancing electromagnetic valve closed and continuously monitoring the change of the oil level height.
In a preferable technical solution of the oil return control method for the refrigeration system, an electric pump is further provided on the second enhanced oil return line and downstream of the second enhanced electromagnetic valve, and when both the first oil level switch and the second oil level switch are closed,
after a first preset time period, controlling the first enhancement electromagnetic valve and the second enhancement electromagnetic valve to be closed;
after a third preset time period, controlling the electric pump to start;
re-detecting an oil level height within the oil separator;
comparing the current oil level height to the second oil level height;
when the current oil level height is smaller than the second oil level height, the second oil level switch is turned off;
after a second preset time period, controlling the second enhancement electromagnetic valve to be disconnected;
and after a fourth preset time period, controlling the electric pump to be powered off. When the first oil level switch and the second oil level switch are both closed, the lubricating oil in the oil separator is excessive at the moment, and the compressor may run in an oil shortage mode, so that oil return needs to be performed timely and quickly. Thus, the first and second intensifier solenoid valves are controlled to close. At this time, three oil return pipelines (a basic oil return pipeline, a first enhanced oil return pipeline and a second enhanced oil return pipeline) are arranged between the oil separator and the compressor, and the oil return rate is obviously increased. In addition, an electric pump is further arranged on the second enhanced oil return pipeline, and when the second enhanced electromagnetic valve is closed, the electric pump is controlled to be started, so that the oil return rate can be further improved. When the newly measured oil level is lower than the second oil level, indicating that the amount of oil in the compressor has been replenished at this time, the second intensifying solenoid valve is controlled to be turned off. And after the fourth preset time period, the electric pump is controlled to be shut down, so that the lubricating oil remained in the second enhanced oil return pipeline can be conveyed to the compressor, and the utilization rate of the lubricating oil is improved.
In a preferred technical solution of the oil return control method for a refrigeration system, after the electric pump is shut down, the oil level height in the oil separator is detected again;
comparing the re-measured oil level height to the first oil level height;
when the oil level height measured again is less than the first oil level height, the first oil level switch is turned off;
and after the second preset time period, controlling the first enhancement electromagnetic valve to be disconnected. When the oil level height measured again is lower than the first oil level height, the oil amount can meet the lubricating requirement of the compressor at the moment, and therefore the first enhancing electromagnetic valve is controlled to be disconnected.
In a preferable embodiment of the oil return control method for a refrigeration system, when the oil level height is measured again and is equal to or greater than the first oil level height, the step of re-detecting the oil level height in the oil separator is repeated. When the oil level height is measured again to be larger than or equal to the first oil level height, which indicates that the lubricating oil in the oil separator is still more, the first enhancing electromagnetic valve is kept closed, and the change of the oil level height is continuously monitored.
In order to solve the problems in the prior art, namely to solve the problem that the refrigeration system in the prior art cannot return oil in time, the invention provides a refrigeration system. The refrigeration system performs oil return by using the oil return control method. By using the oil return control method for the refrigeration system, the refrigeration system can return oil to the compressor in time based on the height of the oil level in the oil separator, so that the oil return opportunity and the oil return amount are more accurate and accord with the actual requirement, and the oil return efficiency is also obviously improved.
Drawings
Preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:
FIG. 1 is a system schematic of an embodiment of the refrigeration system of the present invention;
FIG. 2 is a flow chart of a method of oil return control for a refrigeration system of the present invention;
FIG. 3 is a first partial flow chart of an embodiment of a method of oil return control for a refrigeration system of the present invention;
fig. 4 is a second partial flowchart of the embodiment of the oil return control method for the refrigeration system according to the invention.
List of reference numerals:
1. a refrigeration system; 10. an oil separator; 11. a barrel; 111. a bottom; 112. a side wall; 12. an air inlet pipe; 121. an air inlet; 13. an air outlet pipe; 131. an air outlet; 14. a base oil return port; 15a, a first enhanced oil return port; 15b, a second enhanced oil return port; 16a, a first oil level switch; 16b, a second oil level switch; 21. a compressor; 211. an exhaust port; 212. an air suction port; 213. a high pressure switch; 214. an exhaust pipe; 215. an air return pipe; 22. a condenser; 221. a water outlet of the condenser; 222. a water inlet of the condenser; 23. drying the filter; 24. an expansion valve; 25. an evaporator; 251. a water outlet of the evaporator; 252. a water inlet of the evaporator; 253. a butterfly valve; 26a, a first ball valve; 26b, a second ball valve; 27a, a high-pressure gas pipeline; 27b, a high-pressure liquid pipeline; 27c, a low-pressure liquid line; 27d, a low-pressure gas pipeline; 30. a base oil return line; 301. a first angle valve; 302. a first oil filter; 303. a basic oil return electromagnetic valve; 304. a second liquid sight glass; 305. a second angle valve; 306. an ejector; 306a and an injection end; 306b, an injected end; 306c, an outlet end; 31. a first enhanced oil return line; 311. a first boost solenoid valve; 32. a second enhanced oil return line; 321. a second boost solenoid valve; 322. an electric pump; 33. an auxiliary oil return line; 331. a third angle valve; 332. a second oil filter 333, and a third liquid sight glass.
Detailed Description
Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and are not intended to limit the scope of the present invention.
It should be noted that the terms "first", "second" and "third" in the description of the present invention are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The invention provides an oil return control method for a refrigeration system, aiming at solving the problem that the refrigeration system in the prior art cannot return oil in time. The oil return control method comprises the following steps:
detecting an oil level height within the oil separator during operation of the refrigeration system (step S1);
comparing the oil level height with the first oil level height and the second oil level height (step S2);
controlling on and off of the first oil level switch and the second oil level switch based on the comparison result (step S3);
the closing and opening of the first and second intensification solenoid valves are controlled based on the on-off condition (step S4).
FIG. 1 is a system schematic of an embodiment of the refrigeration system of the present invention. In one or more embodiments, as shown in fig. 1, the refrigeration system 1 of the present invention is a water-cooled chiller. Alternatively, the refrigeration system 1 may be an air-cooled chiller, a multi-connected air conditioner, or other suitable refrigeration system. The refrigeration system 1 includes an oil separator 10, a compressor 21, a condenser 22, an expansion valve 24, and an evaporator 25. The compressor 21 has an exhaust port 211 and an intake port 212. The exhaust port 211 of the compressor 21 is connected to the intake port 121 of the intake pipe 12 of the oil separator 10 through an exhaust pipe 214. The outlet 131 of the outlet pipe 13 of the oil separator 10 is connected to the input of the condenser 22 through a high-pressure gas line 27 a. The output of condenser 22 is connected to expansion valve 24 by high pressure liquid line 27 b. The expansion valve 24 is connected to the input of the evaporator 25 by a low pressure liquid line 27 c. The output of the evaporator 25 is connected to the suction port 212 of the compressor 21 through a low-pressure gas line 27d and a return gas pipe 215 which are connected to each other. The pipes are interconnected to form a main circuit of the refrigeration cycle allowing a refrigerant to flow therein.
As shown in FIG. 1, in one or more embodiments, the compressor 21 is a screw compressor. Alternatively, the compressor 21 may be a centrifugal, piston, or other suitable compressor. A high pressure switch 213 is provided on the compressor 21 to provide shutdown protection for the compressor 21 when the discharge pressure of the compressor 21 exceeds a predetermined value. In one or more embodiments, condenser 22 is a horizontal shell and tube condenser. The condenser 22 is provided with a condenser water outlet 221 which can be communicated with a condensed water outlet pipe and a condenser water inlet 222 which can be communicated with a condensed water inlet pipe. Alternatively, condenser 22 may be a tube-in-tube, a finned coil, or other suitable condenser. In one or more embodiments, a first ball valve 26a is provided in the high-pressure liquid line 27b and positioned downstream of the condenser 22 to control the on/off of the refrigerant in the high-pressure liquid line 27b for ease of maintenance. In one or more embodiments, a dry filter 23 is further disposed in the high-pressure liquid line 27b and positioned downstream of the first ball valve 26a to dry and filter the refrigerant to prevent harmful substances such as moisture and impurities from damaging the functional components. In one or more embodiments, the expansion valve 24 is a thermal expansion valve. Alternatively, the expansion valve 24 may be an electronic expansion valve, a throttle valve, or other suitable expansion valve. In one or more embodiments, a second ball valve 26b is disposed in the low-pressure liquid line 27c and positioned downstream of the expansion valve 24 to control the on-off of the refrigerant in the low-pressure liquid line 27 c. In one or more embodiments, evaporator 25 is a horizontal shell and tube evaporator. The evaporator 25 is provided with an evaporator water outlet 251 which can be communicated with a cooling water outlet pipe and an evaporator water inlet 252 which can be communicated with a cooling water inlet pipe. Alternatively, evaporator 25 may be a tube-in-tube, a finned coil, or other suitable evaporator. In one or more embodiments, a butterfly valve 253 is further disposed between the low-pressure gas line 27d and the gas return line 215 to control the opening and closing of the refrigerant in the low-pressure gas line 27 d.
As shown in fig. 1, in one or more embodiments, the oil separator 10 includes a cartridge 11. The barrel 11 is made of 304 stainless steel or other suitable material to enhance its strength. A base oil return port 14, a first reinforcing oil return port 15a, and a second reinforcing oil return port 15b are provided at the bottom 111 of the cylinder 11 with a space therebetween. The basic oil return port 14 is connected to the air return pipe 215 through the basic oil return line 30, the first enhanced oil return port 15a is connected to the air return pipe 215 through the first enhanced oil return line 31, and the second enhanced oil return port 15b is connected to the air return pipe 215 through the second enhanced oil return line 32. The base return line 30, the first enhancement return line 31 and the second enhancement return line 32 are formed in parallel with each other. In addition, a first oil level switch 16a and a second oil level switch 16b are also provided on the side wall 112 of the barrel 11 to monitor corresponding first and second oil level heights within the oil separator 10, wherein the second oil level height is higher than the first oil level height. It is understood that the first oil level height and the second oil level height may be adjusted through experience or experimentation. In one or more embodiments, the first and second oil level switches 16a, 16b are float-type oil level switches. Alternatively, the first and second oil level switches 16a, 16b may be provided as photoelectric oil level switches, or other suitable oil level switches. First oil level switch 16a and second oil level switch 16b are electrically connected to a control system (not shown in the drawings) of refrigeration system 1, respectively, so as to conveniently obtain on-off signals of first oil level switch 16a and second oil level switch 16 b.
As shown in fig. 1, in one or more embodiments, a first angle valve 301, a first oil filter 302, a base oil return solenoid valve 303, a second fluid sight mirror 304, and a second angle valve 305 are connected in series in the flow direction of the lubricating oil on the base oil return line 30 in this order. The base return solenoid valve 303 is configured to be electrically connected to the control system of the refrigeration system 1 to control the flow of lubricant in the base return line 30 by controlling the on/off and opening of the base return solenoid valve 303. The first oil filter 302 can filter the lubricating oil to remove impurities, thereby ensuring the normal operation of the compressor 21. The second sight glass 304 can monitor the flow condition and moisture content of the lube oil in the base return line 30. The first angle valve 301 and the second angle valve 305 are arranged to facilitate installation and maintenance of the pipeline.
In one or more embodiments, as shown in FIG. 1, a first boost solenoid valve 311 is provided in the first boost return line 31. The first boost solenoid valve 311 is configured to be electrically connected to a control system of the refrigeration system 1, so as to control the on/off of the first boost oil return circuit 31 by controlling the on/off of the first boost solenoid valve 311. In one or more embodiments, a second boost solenoid valve 321 and an electric pump 322 are provided in the second boost return line 32 in sequence along the flow direction of the lubricating oil. The second boost solenoid valve 321 and the electric pump 322 are electrically connected to the control system of the refrigeration system 1.
As shown in fig. 1, in one or more embodiments, an auxiliary return line 33 is also provided between the evaporator 25 and the return air pipe 215. A third angle valve 331, a second oil filter 332, and a third fluid scope 333 are connected in series in this order along the flow direction of the lubricating oil in the auxiliary oil return line 33. Through setting up supplementary oil return line 33, can effectively avoid lubricating oil deposit in evaporimeter 25, improve evaporimeter 25's heat exchange efficiency, can also improve the utilization ratio of lubricating oil. The second oil filter 332 can filter the lubricating oil to improve cleanliness. The third sight glass 333 can be used to monitor the flow state and moisture content of the lubricating oil in the auxiliary oil return line 33. In one or more embodiments, an eductor 306 is also provided in the auxiliary return line 33. The eductor 306 has an eductor end 306a connected to the base oil return line 30, an eductor end 306b connected to the auxiliary oil return line 33, and an outlet end 306c connected to the air return line 215. High pressure jets are formed as the lubricant passes from the base return line 30 through the eductor 306, creating a negative pressure within the eductor 306. The lubricant in the auxiliary return line 33 is sucked out smoothly by the negative pressure, and flows from the outlet end 306c of the ejector 306 to the muffler 215 after being mixed with the jet flow in the base return line 30.
The oil return control method for the refrigeration system according to the present invention will be described in detail below based on the refrigeration system 1 described above. It should be noted that the oil return control method of the present invention may also be used in other suitable refrigeration systems.
Fig. 2 is a flow chart of an oil return control method for a refrigeration system according to the present invention. As shown in fig. 2, when the oil return control method for the refrigeration system of the present invention is started, step S1 is first executed, that is, the oil level in the oil separator 10 is detected during the operation of the refrigeration system 1. Next, the oil level height is further compared with the first oil level height and the second oil level height (step S2). Then, step S3 is executed to control the on/off of the first oil level switch 16a and the second oil level switch 16b based on the comparison result. The closing and opening of the first and second intensification solenoid valves 311 and 321 are controlled based on the on-off condition (step S4).
It should be noted that the term "operation period" refers to an operation period after the start-up period of the refrigeration system is completed. In one or more embodiments, the compressor 21 is provided with a start target frequency (e.g., 40Hz-60 Hz). After the compressor 21 is started, the operation frequency gradually increases according to the set program, and when the operation frequency reaches the start target frequency and lasts for a certain time (for example, 3min), the start-up phase is ended, and the refrigeration system 1 enters the operation phase.
Fig. 3 is a first partial flowchart of an embodiment of an oil return control method for a refrigeration system according to the present invention. The partial flow chart is used for the conventional oil return control of the refrigeration system in the starting-up phase and the running phase. As shown in fig. 3, when the oil return control method for the refrigeration system of the present invention is started, step S5 is executed, and after the compressor 21 is started, the basic oil return solenoid valve 303 is controlled to be closed. Next, the differential pressure of the compressor 21 is detected (step S6). In one or more embodiments, a high pressure sensor is provided on the discharge pipe 214 to detect the discharge pressure of the compressor 21. A low pressure sensor is provided on the muffler 215 to detect the suction pressure of the compressor 21. The pressure difference is the difference between the discharge pressure and the suction pressure. Then, step S7 is executed to control the opening degree of the basic oil return solenoid valve 303 based on the measured pressure difference, so as to realize the conventional oil return control of the refrigeration system 1 during the startup phase and the operation phase. Unless expressly indicated to the contrary, reference herein to "conventional oil return" means that oil return is only via the base oil return line 30.
Fig. 4 is a second partial flowchart of the embodiment of the oil return control method for the refrigeration system according to the invention. The partial flow chart is used for oil return control of the refrigeration system in the operation stage. As shown in fig. 4, during the operation of the refrigeration system 1, the oil level height inside the oil separator 10 is detected (step S1). Next, it is determined whether the oil level height is smaller than the first oil level height (step S21). If the determination result is yes, it indicates that the amount of lubricating oil in the oil separator 10 is small at this time, and the first oil level switch 16a and the second oil level switch 16b are turned off (step 310). Accordingly, the lubricating oil in the compressor 21 is high, and the compressor 21 does not run in an oil shortage mode. Thus, the first and second intensifier solenoid valves 311 and 321 are kept open, and the execution step ends. It can be understood that, in the refrigeration system 1, only the base oil return line 30 is in the open state, and the base oil return solenoid valve 303 adjusts the opening degree based on the pressure difference, so as to perform the conventional oil return control on the compressor 21.
As shown in fig. 4, when step S21 is performed, if the determination result is no, the control method proceeds to step S22, i.e., determines whether the oil level height is equal to or greater than the second oil level height. Wherein the second oil level height is higher than the first oil level height. In one or more embodiments, the second oil level is lower than the corresponding oil level in the oil separator 10 when the oil shortage alarm of the compressor 21 occurs, so as to ensure that the oil returns in time before the oil shortage operation of the compressor 21. If the determination result is no, i.e., the oil level height is between the first oil level height and the second oil level height, the first oil level switch 16a is controlled to be closed (step S320). In this case, the amount of the lubricating oil in the oil separator 10 is large, and accordingly, the amount of the lubricating oil in the compressor 21 is small, and the oil return requirement cannot be actually met only by the base oil return line 30. Therefore, step S420 is executed, and after the first preset time period, the first boost solenoid valve 311 is controlled to be closed, so as to enter the first boost oil return control mode. In one or more embodiments, the first preset time period is 10 s. Alternatively, the first preset time period may be set to be longer or shorter than 10s for other suitable time, such as 8s, 12s, etc. By controlling the first intensifying check solenoid valve 311 to close, the lubricating oil in the oil separator 10 can flow from the first intensifying return port 15a to the return pipe 215 of the compressor 21 along the first intensifying return line 31. In other words, an oil return pipeline is added between the oil separator 10 and the compressor 21, and the oil return efficiency is improved. Then, the oil level height in the oil separator 10 is newly detected (step S421). The measured current oil level height is compared with the first oil level height, and it is determined whether the current oil level height is less than the first oil level height (step S422). If the current oil level height is greater than or equal to the first oil level height, which indicates that the amount of lubricating oil in the oil separator 10 is still large at this time, the first boost solenoid valve 311 is kept closed, and step S421 is repeatedly executed, i.e., the oil level height in the oil separator 10 is re-detected. If the current oil level height is less than the first oil level height, indicating that the amount of lubricating oil in the oil separator 10 has decreased at this time, the first oil level switch 16a is turned off (step S423). Next, the control method proceeds to step S424, and after a second preset time period, the first boost solenoid valve 311 is controlled to be turned off, so that the first boost oil-return control mode is exited. After step S424 is performed, the control method ends. In one or more embodiments, the second predetermined time is 9 s. Alternatively, the second preset time period may also be set to other suitable times longer or shorter than 9s, such as 7s, 11s, etc.
As shown in fig. 4, in executing step S22, if the determination result is yes, i.e., when the oil level height is equal to or greater than the second oil level height, step S330 is executed, with the first oil level switch 16a closed and the second oil level switch 16b closed. When the oil level switch is equal to or greater than the second oil level height, it means that the amount of lubricating oil in the oil separator 10 is excessive at this time, and the compressor 21 runs in an oil shortage state. Next, step S430 is executed, and after a first preset time period, the first boost solenoid valve 311 and the second boost solenoid valve 321 are controlled to be closed. At this time, the first enhancing solenoid valve 311 and the second enhancing solenoid valve 321 are simultaneously closed, and the lubricating oil in the oil separator 10 can flow from the first enhancing oil return port 15a and the second enhancing oil return port 15b to the air return pipe 215 of the compressor 21 along the first enhancing oil return pipeline 31 and the second enhancing oil return pipeline 32, respectively. In other words, with the addition of two oil return lines between the oil separator 10 and the compressor 21, the oil return rate is significantly increased. Then, after a third preset time period, the electric pump 322 is controlled to be powered on, thereby entering a second enhanced oil return control mode. In one or more embodiments, the third preset time period is 15 seconds. Alternatively, the third preset time period may also be set to other suitable times, such as 13s, 17s, etc., longer or shorter than 15 s. By closing the second boost solenoid valve 321 and then controlling the electric pump 322 to start, the electric pump 322 can be prevented from idling, and the normal operation of the electric pump can be ensured. The oil return rate can be further increased by providing an electric pump 322 on the second enhanced return line 32. Control proceeds to step S432 to re-detect the oil level height within the oil separator 10. Next, the current oil level height is compared with the second oil level height, and it is determined whether the current oil level height is less than the second oil level height (step S433). If the determination result is no, indicating that the current oil level height is still higher than the second oil level height, step S432 is repeated, i.e., the oil level height within the oil separator 10 is re-detected. If the judgment result is yes, indicating that the current oil level has decreased, the second oil level switch 16b is controlled to be turned off (step S434). Next, step S435 is executed to control the second boost solenoid valve 321 to be turned off after a second preset time period elapses. Then, after a fourth preset time period, the electric pump 322 is controlled to be powered off, so as to exit the second enhanced oil return control mode. In one or more embodiments, the fourth preset time period is 14 s. Alternatively, the fourth preset time period may be set to other suitable times longer or shorter than 14s, such as 12s, 16s, etc. By turning off the second enhancement solenoid valve 321 and then controlling the electric pump 322 to turn off, the lubricant oil remaining in the second enhancement oil return line 32 can be delivered to the compressor 21, so as to improve the utilization rate of the lubricant oil. After the electric pump is shut down, control proceeds to step S421 to re-detect the oil level in the oil separator 10. Then, it is determined whether the current oil level height is less than the first oil level height (step S422). If the current oil level height is equal to or greater than the first oil level height, the first intensifying solenoid valve 311 is kept closed, and step S421 is repeatedly performed. If the current oil level height is less than the first oil level height, the first oil level switch 16a is controlled to be turned off (step S423). Next, step S424 is executed, and after a second preset time period, the first boost solenoid valve 311 is controlled to be turned off. After step S424 is performed, the control method ends.
It is noted that during the implementation of the first and second enhanced return control modes, the base return solenoid valve 303 is always in a closed state, thus maintaining the return through the base return line 30.
So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the invention, a person skilled in the art may combine technical features from different embodiments, and may make equivalent changes or substitutions for related technical features, and such changes or substitutions will fall within the scope of the invention.
Claims (10)
1. An oil return control method for a refrigeration system, wherein the refrigeration system comprises a compressor and an oil separator, a first enhanced oil return port and a second enhanced oil return port which are spaced from each other are arranged at the bottom of the oil separator, the first enhanced oil return port is connected with an air return pipe of the compressor through a first enhanced oil return pipeline with a first enhanced electromagnetic valve, the second enhanced oil return port is connected with the air return pipe through a second enhanced oil return pipeline with a second enhanced electromagnetic valve, a first oil level switch corresponding to a first oil level height and a second oil level switch corresponding to a second oil level height are further arranged on a side wall of the oil separator, and the second oil level height is higher than the first oil level height, and the oil return control method comprises the following steps:
detecting an oil level height within the oil separator during operation of the refrigeration system;
comparing the oil level height to the first oil level height and the second oil level height;
controlling the on-off of the first oil level switch and the second oil level switch based on the comparison result;
controlling the first and second intensifier solenoid valves to be closed and opened based on the on-off condition.
2. The oil return control method for a refrigeration system according to claim 1, wherein a basic oil return port is further provided at the bottom, the basic oil return port is connected to the air return pipe through a basic oil return line having a basic oil return solenoid valve, and the oil return control method further comprises:
after the compressor is started, controlling the basic oil return electromagnetic valve to be closed;
detecting a pressure difference of the compressor;
and controlling the opening degree of the basic oil return electromagnetic valve based on the pressure difference.
3. The oil return control method for a refrigeration system according to claim 1, wherein the step of controlling the on/off of the first oil level switch and the second oil level switch based on the comparison result includes:
when the oil level height is smaller than the first oil level height, controlling the first oil level switch and the second oil level switch to be switched off;
when the oil level height is greater than or equal to the first oil level height and smaller than the second oil level height, controlling the first oil level switch to be closed and controlling the second oil level switch to be opened;
and when the oil level height is greater than or equal to the second oil level height, controlling the first oil level switch and the second oil level switch to be closed.
4. The oil return control method for a refrigeration system according to claim 3, wherein when both of the first oil level switch and the second oil level switch are turned off,
keeping the first and second intensifier solenoid valves open.
5. The oil return control method for a refrigeration system according to claim 3, wherein when the first oil level switch is closed and the second oil level switch is open,
after a first preset time period, controlling the first enhancement electromagnetic valve to be closed;
re-detecting an oil level height within the oil separator;
comparing the current oil level height to the first oil level height;
when the current oil level height is smaller than the first oil level height, the first oil level switch is turned off;
and after a second preset time period, controlling the first enhancing electromagnetic valve to be disconnected.
6. The oil return control method for a refrigeration system according to claim 5, wherein the step of re-detecting the oil level height within the oil separator is repeated when the current oil level height is equal to or greater than the first oil level height.
7. The oil return control method for a refrigeration system according to claim 3, wherein an electric pump is further provided on the second enhanced oil return line downstream of the second enhanced solenoid valve, and when both the first oil level switch and the second oil level switch are closed,
after a first preset time period, controlling the first enhancement electromagnetic valve and the second enhancement electromagnetic valve to be closed;
after a third preset time period, controlling the electric pump to start;
re-detecting an oil level height within the oil separator;
comparing the current oil level height to the second oil level height;
when the current oil level height is smaller than the second oil level height, the second oil level switch is turned off;
after a second preset time period, controlling the second enhancement electromagnetic valve to be disconnected;
and after a fourth preset time period, controlling the electric pump to be powered off.
8. The oil return control method for a refrigeration system as recited in claim 7 wherein the oil level in the oil separator is re-sensed after the electric pump is shut down;
comparing the re-measured oil level height to the first oil level height;
when the oil level height measured again is less than the first oil level height, the first oil level switch is turned off;
and after the second preset time period, controlling the first enhancement electromagnetic valve to be disconnected.
9. The oil return control method for a refrigeration system according to claim 8, wherein the step of re-detecting the oil level height within the oil separator is repeated when the oil level height is again measured to be equal to or greater than the first oil level height.
10. A refrigeration system, characterized in that the refrigeration system is oil-returned using the oil return control method according to any one of claims 1 to 9.
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Application publication date: 20211001 |